JPH075363A - Non-coaxial confocal polyhedral reflection optical system - Google Patents

Abstract

(57) [Abstract] [Purpose] A large number of reflecting surfaces can be combined, many variable parameters can be introduced, and a wide field of view can be obtained by using a combination of a quadric surface with a focal point. A high-resolution reflective optical system is provided. [Structure] The first surface S1 as an entrance surface is a paraboloid of revolution, the second surface S2 is an ellipsoid of revolution, and the third surface S3 is a hyperboloid of revolution. The position of the exit focal point F1 'of the first surface S1 and the entrance focal point F2 of the second surface S2, and the exit focal point F2' of the second surface S2.
And the position of the incident focal point F3 on the third surface S3 are confocal at the same position. Further, the rotational symmetry axes F1-F1 ', F2-F2', F3-F3 'of the respective surfaces S1, S2, S3 are arranged not coaxially but coaxially. Then, when light from a sufficiently distant point is incident off-axis on the paraboloid of revolution of the first surface S1,
The optical image is formed in the vicinity of the exit focal point F3 'on the third surface S3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wide-field, high-resolution reflective optical system.

[0002]

2. Description of the Related Art An image forming optical system has a function of collecting sunlight reflected from an object or infrared light emitted from the object itself to form an image of the light. Also, the afocal optical system is used in combination with some kind of imaging optical system,
Like an imaging optical system, it has the function of forming an image of the light of an object.

As an optical system of this kind, a system having a wide field of view, high resolution, a wide wavelength range, a large aperture, bright, easy processing and capable of forming a plane straight line image has been long sought. .

By the way, the optical system is roughly classified into a refracting optical system using a refracting material such as a lens and a reflecting optical system using a reflecting surface such as a metal.

Table 1 shows a comparison of advantages and disadvantages of the refractive optical system and the reflective optical system.

[0006]

[Table 1]

As can be seen from this table, even though the reflection optical system has many advantages, like the astronomical telescope,
It is used only for special applications with a narrow field of view (for example, 1 degree or less), and many cameras and the like are refractive optical systems. It is considered that this is simply due to the narrow field of view of the reflective optical system.

Then, why is it possible to design the reflective optical system to have a narrow visual field and the refractive optical system to have a wide visual field? This can be considered as follows.

In the refracting optical system, light travels in one direction along the optical axis, and a combination of many lenses can be easily constructed.
Therefore, it is possible to combine a large number of various parameters such as a combination of many spherical surfaces with different curvatures (or an aspherical surface based on a spherical surface), a combination of various surface intervals, and a combination of materials with different refractive indexes. There are many parameters that can be changed, and if the combination is properly designed, a wide image format surface without blurring can be created even in the periphery, and a high resolution optical system can be realized over a wide field of view.

On the other hand, since the reflection optical system is a reflection phenomenon, the light ray does not travel in one direction along the optical axis, but travels in the opposite direction with each reflection, and is reflected in Newton, Cassegrain, Gregory type reflection optical system, etc. As typified by the conventional coaxial arrangement,
I couldn't combine many faces, and at most I could only combine two. Therefore, the number of parameters that can be changed is small, the aberration cannot be corrected over a wide range of the image format surface, and the wide-field reflective optical system cannot be designed.

[0011]

In summary, although the reflective optical system has many advantages, many parameters cannot be changed in the conventional coaxial arrangement having the optical axis, and therefore the number of parameters that can be changed is small. The aberration could not be corrected. Therefore, it can be said that only a high-resolution area near the optical axis can be used, the field of view becomes narrow, and it can only be used for special purposes.

Therefore, in the conventional reflection optical system, since the reflection surfaces are coaxially arranged and used, it is possible to combine only a few pieces at most, and the aberration is corrected and the processing is easy in the wide-field high-resolution reflection optical system. I couldn't design the system.

Therefore, the present invention makes it possible to combine a large number of reflecting surfaces by eliminating the conventional coaxial (optical axis), thereby introducing many variable parameters and guiding principles. As a reflection curved surface to be used, not as an arbitrary curved surface, a combination of a rotation paraboloid, a rotation ellipsoid, a rotation bilobular hyperboloid, a spherical surface, and a plane (hereinafter referred to as a focused quadric surface) as a reflection curved surface to be used. The purpose of the present invention is to provide a catoptric system with a wide field of view and high resolution.

[0014]

In order to achieve the above object, a non-coaxial confocal polyhedral reflecting optical system according to claim 1 uses a plurality of curved surfaces having a focal point, and a part of the curved surfaces is a reflecting surface. And each reflecting surface has an axis of rotational symmetry, at least one of the individual axes of rotational symmetry is arranged not to lie on one fixed straight line and the focal point of any curved surface and its The feature is that the focal points of the front and rear curved surfaces are placed at the same position. Further, in claim 2, the first incident surface of the curved surface is a paraboloid of revolution. Further, in the afocal reflection optical system according to the third aspect, the first incident surface and the last exit surface of the curved surface are rotation paraboloids. Further, in claim 4, the curved surface is slightly deformed from the surface based on the surface shape having the focus.

[0015]

It is well known that one of the spheroidal surfaces and the rotating bilobed hyperboloids used as the curved surface of the present invention has two different focal points. If it is considered that the paraboloid of revolution also has another focus at infinity in addition to the normal focus, it can be considered as a plane having two different focuses. Further, the spherical surface has one focal point, and the flat surface is considered to be a focal point everywhere. Here, the focus is a geometrical optical meaning of a real or imaginary point light source due to a reflecting surface,
It is a point peculiar to the reflecting surface that is exactly a real or imaginary point image.

If there is an object near the focal point of a certain quadric surface with a focal point, its optical image, including the real image and the virtual image, should also be near the other focal point of the curved surface. This is because, in a quite strict sense, a light beam emitted from or directed to a focus is focused on or diverged from another focus, that is, an exact point image of real or imaginary is formed, and , Since this action is performed continuously, if there is a strict point image correspondence between the object-side focus and the image-side focus, even in the vicinity of the focus, the image can still be in the vicinity of the focus without considering the degree of blurring. Because. If the unblurred neighborhood of this image is fairly wide,
Since the aberration has been corrected, a wide field of view can be achieved. It should be noted that the correction of aberration means that an allowable range is indicated depending on the application in which the optical system is used, and is not a general and strict determination, and always includes a certain allowable range.

As described above, a single plane is considered, but a large number of focal points 2
By constructing the quadric surface while focusing on the front and back surfaces,
The above discussion holds true. That is, by making the confocal point, the configuration of the reflective optical system in which spherical aberration in the narrow sense is completely removed can be guaranteed, and the image generating action is continuously performed. A light image is formed in the vicinity of the exit focal point, and it is possible to design by expanding many parameters in the vicinity without blurring by changing many parameters. Also, it is possible to change many parameters easily by making the reflecting surface non-coaxial. In the present invention, a large number of reflective surfaces having a wide field of view and high resolution are configured by arranging a large number of reflective surfaces having a focal point confocally in the front and rear, and arranging them non-coaxially. Here, the non-coaxial arrangement means an arrangement in which each surface has a rotational symmetry axis, but does not coincide with one straight line which is also one of the rotational symmetry axes.

For reference, the Newton-Cassegrain-Gregory reflection optical system described above is a confocal optical system, but it is not a coaxial optical system but a coaxial optical system having an optical axis. I will add it.

It is empirically known that aberrations cannot be corrected only by a convex lens or a concave lens in a refractive optical system. Aberration can be corrected for the first time by combining a convex lens and a concave lens having mutually opposite actions. According to the theoretical analysis by the inventors, the inner reflection of the ellipsoid and the outer reflection of the hyperboloid have the same action, and the surface having the opposite action is the outer reflection of the ellipsoid and the inner reflection of the hyperboloid. I know that there is. That is, aberrations can be corrected by combining a large number of elliptic surfaces and inner and outer surfaces of the hyperboloids as reflecting surfaces.

When the object is sufficiently far away, the incident surface should be a paraboloid whose focus is considered to be at infinity. In the afocal system, the incident surface and the exit surface should be rotational paraboloids. It is composed of faces.

Like the curved surface used for the entrance surface of the reflective Schmidt optical system, aspherical surface processing without a rotational symmetry axis is still difficult to process in modern times, but a parabolic surface used in the present invention as a curved surface with a focus, Elliptical surfaces and hyperboloids are aspherical surfaces, but they have an axis of rotational symmetry, and even the processing of surfaces that are far from that axis is easy to process in modern times when ultra-precision processing technologies such as diamond turning have matured. is there.

In order to reduce the number of surfaces in a refracting optical system, an aspherical surface based on a spherical surface is often introduced into a small number of surfaces. In the present invention, this idea is applied to construct a reflecting optical system. The number of curved surfaces can be reduced.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of an image forming type non-coaxial confocal reflection optical system having a three-sided structure according to the present invention.

The reflective optical system according to this embodiment is composed of three quadric surfaces with a focal point, and in the figure, S1 is an incident surface and the first surface is a paraboloid of revolution, S2. Is a spheroid of the second surface, and S3 is a hyperboloid of rotation of the third surface. Further, F1 is the first surface S1 existing at infinity.
, F1 'is the exit focal point of the first surface S1. Similarly, F2 is the entrance focal point of the second surface S2, F2 'is the exit focal point of the second surface S2, F3 is the entrance focal point of the third surface S3, and F3' is the exit focal point of the third surface S3.

The exit focal point F1 'of the first surface S1 and the entrance focal point F2 of the second surface S2 are at the same position. Similarly, the exit focal point F2 'of the second surface S2 and the entrance focal point F3 of the third surface S3 are in the same position and are in a confocal relationship, and the optical image is the third focal point.
It is formed near the exit focal point F3 'of the surface S3.

The axis of rotational symmetry is the parabolic surface S1 of the first surface and F1-
F1 ', F2-F2' on the elliptical surface S2 of the second surface, and F3-F3 'on the hyperboloid S3 of the third surface, and these axes are not coaxial,
It is arranged non-coaxially. Further, βji is an angle formed by the rotational symmetry axis of the i-plane (i is an integer) and the j-plane following the i-plane.

It should be noted that the inner reflection of the ellipsoid and the outer reflection of the hyperboloid have the same effect, and it is understood that the surfaces having the opposite effect are the outer reflection of the ellipsoid and the inner reflection of the hyperboloid. Therefore, aberrations can be corrected by combining a large number of elliptical surfaces and inner and outer surfaces of hyperboloids as reflecting surfaces. As a combination thereof, in the case of a two-sheet configuration, the inside reflection of an ellipsoid and the outside reflection of an ellipsoid, the inside reflection of a hyperboloid and the outside reflection of a hyperboloid, the inside reflection of an ellipsoid and the inside reflection of a hyperboloid, the ellipsoid There are four possibilities: outer reflection and hyperbolic outer reflection.

In the catoptric system constructed as described above, light from a sufficiently distant position (parallel light) is incident off-axis on the first paraboloid S1 of revolution, and then the exit focal point of the paraboloid S1. F
Focused on 1 '. The exit focal point F1 'and the entrance focal point F2 of the spheroidal surface S2 of the second surface are located at the same position, and the light is reflected by the elliptic surface S2 and exit focal point F2' which is another focal point of the elliptic surface S2. Try to get together.

On the other hand, F3, which is the outer focal point and the incident focal point of the rotating hyperboloid S3 of the third surface, is the exit focal point F2 'of the elliptical surface S2.
Are placed at the same position as, and the light flux to be collected is reflected inside the hyperboloid S3 before being condensed by the ellipsoid S2,
An image is formed at F3 'which is the inner focal point and the outgoing focal point of the hyperboloid S3.

Normally, if there is an optical axis, the image can be made perpendicular to the optical axis, but in the present embodiment, it cannot be said that it can be said that the image can be made perpendicular to the axis because it is not coaxial.

In general, the curved surface shape of the quadric surface with focus is expressed as ρ (θ) = L / (1 + ε · cos (θ)) in the curved coordinates with the focal point as the origin. Here, L is the vertical length (a parameter that determines the inner reflection or the outer reflection and represents the size of the curved surface), ε
Is the eccentricity (which determines the type of curved surface and inner or outer reflection).

In this embodiment, since three curved surfaces are arranged in a non-coaxial, confocal relationship in a multifaceted manner, not only can the eccentricity and the vertical length of each surface be changed, but also the angle βji formed by the axes. (Corresponding to the surface spacing of the refracting optical system) can also be changed.

Further, like the curved surface used for the entrance surface of the reflective Schmidt optical system, aspherical surface processing without a rotational symmetry axis is still difficult in modern times, but it is used as a curved surface with a focus in this embodiment. Object surfaces, ellipsoids, and hyperboloids are aspherical surfaces, but they have an axis of rotational symmetry, and even surfaces far away from the axis can be easily processed by using ultra-precision processing technology such as diamond turning. be able to.

Further, in the conventional reflection optical system of the Newton type or the like arranged coaxially, the second reflecting surface and its support worked as a light shielding plate, which was a problem as an imager in the infrared region. In the reflective optical system, since the curved surfaces are arranged non-coaxially, there is no support for blocking light in the total luminous flux, which is also suitable for an infrared imager.

If the object is sufficiently far away, it is necessary to use a parabolic surface whose focal point is considered to be at infinity as the incident surface. In addition, in the afocal reflection optical system, the incident surface is The exit surface is a paraboloid of revolution.

Further, in order to reduce the number of surfaces in the refracting optical system, an aspherical surface based on a spherical surface is often introduced into a small number of surfaces, but in this embodiment, this idea is applied to focus. That is, a quadric surface with focus: a paraboloid of revolution, an ellipsoid of revolution, a hyperboloid of revolution, a sphere, and a plane, and the surface is basically deformed to form a reflective optical system. Thus, the number of curved surfaces can be reduced.

By the way, in the present embodiment, the curved surface used has a three-sided structure, but if the curved surface has the above-mentioned non-coaxial confocal arrangement, it can be composed of any number of surfaces and can be changed accordingly. The number of parameters also increases, and it is possible to design a catoptric system that does not have aberrations up to the periphery of the image format surface.

Further, in the present embodiment, all the three rotational symmetry axes are included in the two-dimensional plane (the real paper surface),
The axes of rotational symmetry may be arranged three-dimensionally.

[0039]

According to the present invention, since it is non-coaxial with no optical axis, many surfaces can be introduced, and by arranging confocal reflecting surfaces having a focal point on the front and rear surfaces, a spherical surface in a narrow sense can be introduced. The configuration of the optical system in which aberration is completely removed is guaranteed. Also,
There are many parameters that can be changed, and a reflective optical system with a wide field of view and high resolution can be designed.Because of the reflective type, the wavelength range that can be used is naturally wide and it is easy to process even large diameters. It is also possible to design an anastigmat reflective optical system that is bright and can obtain a plane linear image.

Further, since all the surfaces used in the present invention have the axis of rotational symmetry, even an aspherical surface can be easily processed by using modern ultra-precision processing technology.

Further, since the conventional Newton type reflection optical system is coaxial, the second reflection surface and its support work as a light shielding plate, and it is said that there is a problem as an imager in the infrared region. Since the catoptric system of the present invention is non-coaxial, there is no support or the like for blocking light in the total luminous flux, and it is also suitable for infrared imagers.

Further, it is possible to reduce the number of curved surfaces to be used by slightly deforming the surface having a focus as a basic shape.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an image forming type non-coaxial confocal polyhedral reflecting optical system having a three-sided structure according to the present invention.

[Explanation of symbols]

S1 ... Rotating paraboloid (first surface), S2 ... Spherical ellipsoid (second surface)
Surface), S3 ... Rotating hyperboloid (third surface), F1 ... First surface entrance focus, F1 '... First surface exit focus, F2 ... Second surface entrance focus, F2' ... Second surface exit Focus, F3 ... Incident focus of third surface, F3 '... Exit focus of third surface, F1-F1' ... Rotational symmetry axis of first surface, F2-F2 '... Rotational symmetry axis of second surface, F3-F
3 '... rotational symmetry axis of the 3rd surface.

Claims (4)

[Claims] 1. A plurality of curved surfaces having a focal point are used, and a part of the curved surfaces is used as a reflecting surface, each reflecting surface having a rotational symmetry axis, and at least one of the individual rotational symmetry axes is A non-coaxial confocal multi-facet reflection optical system characterized in that the focal point of an arbitrary curved surface and the focal points of curved surfaces before and after the curved surface are placed at the same position in a certain fixed straight line arrangement. 2. The non-coaxial confocal polyhedral reflecting optical system according to claim 1, wherein the first incident surface of the curved surface is a paraboloid of revolution. 3. The non-coaxial confocal polyhedral reflecting optical system according to claim 1, wherein the first entrance surface and the last exit surface of the curved surface are rotation paraboloids. 4. The non-coaxial confocal polyhedral reflection optical system according to claim 1, wherein the curved surface is basically a surface having a focal point and is slightly deformed from the surface.